Since the early 1990's, the use of infusion pumps to continuously administer anesthetic medications has been common practice for achieving long term continuous regional anesthesia (such pumps are sometimes referred to as “pain-pumps”). These pumps are either electro-mechanical pumps or mechanical pumps, most of them designed to be ambulatory, utilizing a carrying pouch or similar means.
Post-operative patients and some oncology patients are among those who may require continuous regional anesthesia, which can be achieved by the steady infusion of an analgesic medication, supplied subcutaneously and/or submuscularly by means of an infusion pump connected to a designated catheter. The designated catheter is connected to the patient, who normally receives a dosage of about 2 ml/hr to 12 ml/hr therethrough.
Postoperative patients may suffer severe pain, for example, as a result of movements or of unpredictable incidence. Such severe pain is addressed either by complementary medications or by adding additional anesthetic medication doses.
Currently, there are two main clinical procedures that are used for continuous long terms regional anesthesia. The first method is Surgical Site Infiltration (SSI, or sometimes called Wound Bathing), in which the medication is introduced into or near to the surgical incision by the use of a catheter with a long fenestrated segment inserted into the patient body tissue. The second method is Continuous Peripheral Nerve Block (CPNB), in which the medication is introduced close to the main nerve that controls the area of the pain source (mainly, the area of the surgical incision).
Some pumps are equipped with a Patient Control Analgesia (PCA) device that enables the patient to administer additional medication to deal with severe pain. When the PCA device is activated, a relatively large medication volume (bolus) is injected at a relatively high flow-rate. In parallel PCA administration (the most common version), the bolus medication is in addition to the pump basal flow. In in-line (series) administration, only the bolus medication is delivered. Efficient pain blockage is achieved once the nerve cord is fully circulated with the anesthetic medication. Fully circulated medication spread over the nerve cord is achieved with bolus' flow rate of at-least 5 ml/minute to 6 ml/minute, while the volume of medication delivered is typically between 4 ml to 10 ml, depending on the specific nerve that is being blocked.
As a result of the high hydraulic resistance of a typical Nerve Blocking (NB) catheter, the maximum bolus flow rate of the prior art infusion pumps is about 1.0 ml/minute to 1.5 ml/minute.
Furthermore, prior art mechanical devices fail to efficiently and safely prevent parallel continuous flow through the bolus unit when not being activated. Moreover, the designs of prior art mechanical devices fail to be intuitively activated by those out-patients who have been trained only shortly after being released from the recovery room and don't recall how to activate the bolus unit.